硼氮掺杂的碳纳米管对硫化氢气敏性能的理论研究

应用密度泛函理论研究了纯(8, 0)单壁碳纳米管(SWCNT)和B原子、N原子以及BN原子对掺杂的(8, 0) SWCNTs对硫化氢气体分子的传感性质. 计算结果表明, 与纯碳纳米管相比, B原子掺杂的SWCNT显示了对H₂S分子的敏感性, 其几何结构和电子性质在吸附H₂S分子后发生了显著变化; 而N原子和BN原子对的掺杂没有改善SWCNT对H₂S分子的吸附性能, 因此我们建议B原子掺杂的SWCNT作为检测H₂S分子的新型气相传感器.     

B掺杂SWCNT表面吸附DNA碱基的理论研究

采用基于密度泛函理论的LDA (PWC)方法对比研究了纯单壁纳米碳管(SWCNT)和B掺杂单壁碳纳米管(B doped SWCNT)表面吸附DNA碱基(腺嘌呤)A、(胸腺嘧啶)T、(胞嘧啶)C、(鸟嘌呤)G的吸附特性和本质, 计算研究了最佳吸附位点, 吸附能, 以及稳定吸附模型的电子结构. 结果表明掺杂元素B的引入不会造成SWCNT的结构畸变, 可以局部影响碳纳米管的电子结构, 有效增强SWCNT与DNA碱基之间的电子相互作用, DNA碱基以化学吸附的形式修饰在B掺杂SWCNT的表面. 研究结果预示B掺杂SWCNT表面修饰DNA碱基有潜力成为DNA生物传感器生物识别界面的主要成分.     

钴掺杂氮化硼纳米管吸附氯酚类污染物的理论研究

氯酚(CPs)类污染物是形成持久性有机污染物二噁英的先驱物, 具有较强的致畸、致癌和致突变性. 为探索去除或检测这类污染物的新型材料, 应用密度泛函理论研究了(8,0)单壁氮化硼纳米管(BNNT)和Co掺杂的(8,0)单壁氮化硼纳米管(Co-BNNT)对2-氯酚(2-CP)、2,4,6-三氯酚(TCP)、五氯酚(PCP)的吸附行为及作用机制. 结果表明, 与BNNT相比, Co-BNNT费米能级附近出现杂化态, 带隙明显减小. BNNT对2-CP、TCP和PCP呈现物理吸附, 而Co-BNNT对三种氯酚则是化学吸附, 纳米管与分子间发生了明显的电荷转移, 体系态密度在费米能级附近发生了明显变化. Co原子掺杂明显增强了BNNT的电子输运能力, 提高了纳米管对氯酚的吸附活性. Co-BNNT有望是去除或检测氯酚类污染物的潜在资源.     

Pt掺杂碳纳米管吸附气体小分子的DFT计算

利用B3LYP/LANL2DZ方法对Pt掺杂(5,5)单壁碳纳米管(SCNT)吸附SO₂, HCHO和CO₂三种气体小分子进行了详细的理论计算. 通过分析吸附气体分子前后Pt掺杂SCNT的几何结构、电子态密度变化、前线轨道成分HOMO-LUMO能隙和红外光谱特征, 给出了SCNT-Pt是否有潜力检测这三种气体分子的理论依据.     

硅掺杂的氮化硼纳米管对氯化氰吸附性能的理论研究

为了探索氮化硼纳米管(BNNT)在化学传感器件领域的潜在应用,我们利用密度泛函理论研究了(8,0)单壁BNNT和硅掺杂的(8,0)BNNT对毒性气体氯化氰分子(ClCN)的吸附性能.结果表明,硼位或氮位硅掺杂的BNNT,均对ClCN分子存在较强的化学吸附,而纯氮化硼纳米管对ClCN仅有较弱的物理吸附.态密度的计算进一步表明硅掺杂使纳米管费米能级附近的电子结构发生显著变化,由于杂化态的引入,使带隙明显减小,增强了对毒性ClCN分子的吸附敏感性.硅掺杂的BNNT有望成为检测毒性ClCN分子的潜在资源.     

B、N原子掺杂超长扶手椅型碳纳米管的GTOs-PBC方法研究

使用密度泛函B3LYP/3-21G*方法,并用周期边界条件模型,计算了B、N掺杂纳米管的结构参数、掺杂能量、能带结构和能隙.研究表明,碳纳米管掺杂B、N原子后,能隙均增大,变为半导体.B原子掺杂的碳纳米管具有直接带隙,而N原子掺杂则具有间接带隙,B掺杂的(6,6)和(9,9)管以及N掺杂的(6,6)和(9,9)管的能隙...     

贵金属原子与点缺陷石墨烯的键增强作用

通过密度泛函理论研究了Ag、Au、Pt原子在完美和点缺陷(包括N掺杂、B掺杂、空位点缺陷)石墨烯上的吸附以及这些体系的界面性质.研究表明Ag、Au不能在完美的石墨烯上吸附,N、B掺杂增强了三种金属与石墨烯之间的相互作用.而空位点缺陷诱发三种金属在石墨烯上具有强化学吸附作用.通过电子结构分析发现,N掺杂增强了Au、Pt与C形成的共价键,而Au、Ag与B形成了化学键.空位点缺陷不仅是金属原子的几何固定点,同时也增加了金属原子和碳原子之间的成键.增强贵金属原子和石墨烯相互作用的顺序是:空位点缺陷>>B掺杂>N掺杂.     

空位和B掺杂对Si在石墨烯上吸附的影响

利用基于密度泛函理论的第一性原理计算了空位和B替位掺杂对Si在石墨烯上吸附的影响. 结果表明: 对完整的石墨烯结构, Si吸附在桥位最稳定, Si吸附改变了石墨烯中C原子的自旋性质; 空位和B替位掺杂均加强了Si在缺陷处的吸附, 空位对Si在石墨烯上吸附的影响相对较大; B掺杂改变了Si的稳定吸附位置(由桥位移到顶位); Si在空位和B掺杂石墨烯上吸附, 体系不具有磁性; B掺杂提高了石墨烯体系的导电性能; 单空位缺陷不易形成, 结构不稳定, B掺杂结构相对较稳定.     

H2分子在碱金属掺杂碳纳米管上的吸附特性

采用密度泛函理论研究了H₂在碱金属(M=Li, K)掺杂的扶手椅型单壁碳纳米管上的吸附. 对于碱金属管内掺杂, 模拟了4种氢吸附构型; 对于管外掺杂, 考虑了两种吸附结构, 同时还考虑了两种不同的掺杂浓度. 所有吸附模型都进行了全优化. 计算结果表明, 碱金属掺杂后, 碱金属与碳纳米管之间发生电子授受作用使得碱金属带正电荷, 对于金属Li, 管内掺杂更有利于电子向碳纳米管转移; 与管内掺杂相比, Li原子的管外掺杂更有利于H2分子吸附. 碱金属管外掺杂的碳纳米管吸附H₂的最稳定结构, 存在碱金属原子与H₂分子的配位作用.     

B和N原子掺杂超长(3,3)单壁碳纳米管的从头算研究

用从头算的周期边界条件方法,建立了(3,3)型超长单壁碳纳米管的新模型.使用B3LYP/3-21G方法计算了B和N掺杂纳米管的结构参数、掺杂能量、能带结构以及能隙.研究表明,B和N原子掺杂的(3,3)型单壁碳纳米管具有直接带隙半导体特征,其α轨道计算所得能隙值分别为1.797和2.041 eV.     

HEPT类化合物的QSAR研究

为定量结构／活性相关性研究提取了量子化学参数,拓扑指数Am,分子连接性指数^mxt及疏水性常数,同时应用正交变换和最佳变量子集算法（Leaps-and-Bonds)进行了变量压缩和选择,进而实施了多元回归分析,并由此结果进行了HEPT类化合物（1－[(2-hydroxyethoxy)methyl]-6-(phenylthio)-thymine derivatives)的结构／活性关系的理论解释,进行了人工神经网络法对于该类化合物的活性预测,其结构明显好于多元回归法。     

Effect of the pH of the medium on the chemical shifts in the PMR spectra and on the distribution of the π-electron density

The dependence of the chemical shifts of the ring protons on the pH of the medium for a number of 4-hydroxyquinoline derivatives was studied by means of PMR spectroscopy. The dipolar and uncharged hydroxy forms exist in equilibrium in aqueous solutions. The effect of intramolecular hydrogen bonding on the character of the dependence of the chemical shift on the pH of the medium in the case of 3-piperidinomethyl-4-hydroxyisoquinoline was investigated. The possibility of the separate protonation of the ring nitrogen and the side-chain nitrogen in 3-piperidinomethyl-4-hydroxyisoquinoline was established. The distribution of the -electron density in 4-hydroxyisoquinoline is in good agreement with its chemical behavior.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1546–1549, November, 1971     

Effect of the pH of the medium on the chemical shifts in the PMR spectra and on the distribution of the π-electron density

The dependence of the chemical shift of the ring protons on the pH of the medium for a number of 3-hydroxyquinoline derivatives was studied by PMR spectroscopy. The regions of ionization of the molecules, which correspond to the ranges of acidic, neutral, and alkaline media, were found. In D₂O, 3-hydroxyquinoline is present only in the uncharged hydroxy form. The presence of intramolecular hydrogen bonding in 4-dimethylaminomethyl-3-hydroxyquinoline has a substantial effect on the character of the dependence of the chemical shift on the pH of the medium; the existence of separate protonation of the nitrogen atoms of the ring and the side chain of 4-dimethylaminomethyl-3-hydroxyquinoline was established. The distribution of the -electron density in the 3-hydroxyquinoline molecule is in good agreement with its chemical behavior during electrophilic substitution.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1540–1545, November, 1971.     

液滴荧光传感与计算机联用技术在微量分析中的应用

通过在LS55型荧光-磷光-发光分光光度计上加装液滴产生及调节附件,采用计算机采集与分析处理数据,成功地研制了双通道液滴光化学传感装置.利用葡聚糖凝胶对复合维生素B中不同组分的选择性吸附来达到分离与同时检测的目的,并将其用于复合维生素B药片的分析,取得了满意的结果.     

On the theory underlying the Car-Parrinello method and the role of the fictitious mass parameter

The theory underlying the Car-Parrinello extended-Lagrangian approach to ab initio molecular dynamics (CPMD) is reviewed and reexamined using "heavy" ice as a test system. It is emphasized that the adiabatic decoupling in CPMD is not a decoupling of electronic orbitals from the ions but only a decoupling of a subset of the orbital vibrational modes from the rest of the necessarily coupled system of orbitals and ions. Recent work [J. Chem. Phys. 116, 14 (2002)] has pointed out that, due to the orbital-ion coupling that remains once adiabatic decoupling has been achieved, a large value of the fictitious mass mu can lead to systematic errors in the computed forces in CPMD. These errors are further investigated in the present work with a focus on those parts of these errors that are not corrected simply by rescaling the masses of the ions. It is suggested that any comparison of the efficiencies of Born-Oppenheimer molecular dynamics (BOMD) and CPMD should be performed at a similar level of accuracy. If accuracy is judged according to the average magnitude of the systematic errors in the computed forces, the efficiency of BOMD compares more favorably to that of CPMD than previous comparisons have suggested.     

From the Micro- to the Macro-: Managing the Conservation of the Warship,Vasa

Sweden's famous warship, Vasa, sank on her maiden voyage in August 1628, and remained on the bottom of Stockholm harbour for 333 years. Raised in 1961, she became the first large-scale wooden object to be treated with polyethylene glycol (PEG). In the summer of 2000 a number of acidic salt precipitations were noticed on the surface of the ship and on wooden artefacts in the storerooms. An international research project has been established to look into the causes of this problem and suggest possible re-treatments. Meanwhile projects are underway to monitor movements in the ship, to build a better support system, and to replace the thousands of iron bolts holding the structure together, while a sophisticated new climate system has recently been installed in the museum.